System of motor control.



PATBNTBD SEPT. 10, 1907.

W. H. POWELL.

SYSTEM 01- MOTOR OUNTROL.

APPLICATION FILED D150. 1B, 1908.

00., mumuarou, n. c.

UNIT ED STATES WILLIAM ll. POWELL, ()l NOHWOUI), Ullll),

PATENT OFFICE.

ASSIUNUR Tl) ALLlS-lllli\LME-RS COMPANY, A

(FUltlUltAllUN 01* NEW JERSEY, AND Till) lillLLUUli llLl llfiTlllUMANUFACTURING COM- PANY, A ()OlllOllAllUN Ul OHIO.

SYSTEM OF MOTOR CONTROL.

Specification of Letters Patent.

Patented Sept. 10, 1907.

To all 'u hom it may comm-n:

lie it known that I, \NILLIAM ll. Penance, citizen of the United States,residing at Norwood. in the county of Hamilton and State of Ohio, haveinvented certain new and useful Improvements in Systems of Motor Gentrol, of which the following is a full, clear, and exact specification.

My invention relates to motor control systems and particularly tocontrol systems for mill and hoisting motors.

ln rolling mills and in hoisting machinery, it is necessary that themoving parts be quickly and often reversed.

It is the object of my invention to provide a system in which this canbe readily accomplished and in which the speed of the moving parts maybe varied within wide limits. r

With these objects in view my invention in one of its aspects comprisesthe method of controlling the speed and direction of an electric motorwhich consists in supplying its armature rein two sources of current inseries, said sources heing normally approximetely equal and opposite,and inversely varying the electroinotive forces of said two sources ofcurrent.

In another aspect my invention comprises the method of reversing anelectric motor, which consists in supplying its armature from twoassisting sources oi current in series, then diminishing reversing andincreasing the electromotive force of one of said sources until it issubstantially equal and opposite to that of the other source and thendiminishing, reversing and increasing the electromotive force of theother source.

From another point of view my invention consists of a motor controlsystem comprising a motor, two sources of current connected in seriesfor supplying the motor armature, and means ior varying and reversingthe electromotive force of each of said sources of current.

In still another aspect my invention consists of a System of mdtorcontrol comprising a motor, two generators connected in series forsupplying the armature of said motor, and means for inversely varyingthe field strengths of said generators and for reversing the field whichis weakened.

In still a more specific aspect my invention consists of a system ofmotor control comprising a source of current, a motor supplied thereby,a flywheel mechanically connected to said motor, two generators drivenby said motor and connected in series to supply a second motor, andmeans for inversely varying the field strengths of said generators andfor reversing the field of either of them.

0 Lhor ieatures ol' my invention will appear from the followingdescription and accompanying drawing and will be particularly pointedout in the claims.

The single figure oi the drawing shows diagrammatically one embodimentoi my invention.

In this figure A an electric motor of the threephase induction type,though obviously other forms of motors could be used instead. in therotor circuit of this motor is a starting resistance 1 adjustable bymeans of ashort-circuiting bar 2, and a regulating resistance 3 arrangedto be cut in and out by a solenoid switch 4, which in turn is responsiveto the current strength in the primer circuit of the motor, as through aseries transformer 5. Other means for varying the speed of the motor Amay he used if desired. Two generator armatnres W and B are driven bythe motor A, being preferably directly connected thereto, and on thecommon shaft of the motor A and generators B and B is a heavy lly-WheelC. The two generator armatures are connected in series and supplycurrent to the armature I} of the working motor. The electro motiveforce impressed on the armature D is the algehraic sum oi theeiectromotive forces of the two genorator armatnres B and B The motor I)may be used to drive any desired machinery.

The field winding b and b of the generators and a of the working motorare supplied from any direct current source through a switch 6. Themotor field coil (I may be adjusted by a rheostat 7. The two field coilsof the generators are controlled by a single controller H, which isarranged in different parts of its movement to inversely vary theresistances in circuit respectively nith these two field coils, to thecurrent in either field coil after the current in that field coil hasbeen reduced to a predetermined value, and to vary the resistance incircuit with either one of said field coils alone. The arm or handle hof this controller is divided into several electrically distinct parts.There are two sets of variable resistances, one set of which,resistances 14 and 15, are for the field circuit b, and the other set,16 and 17, for the field circuit 5 The connections of these variousresistances are clearly shown in the drawing.

If desired instead of having the resistances l4 and i5 separate, thecontacts of one may be connected to the corresponding contacts of theother, one of these resistances being omitted. A similar crossconnection may be applied to the contacts of resistances l6 and 17.

The controller H is arranged so that when its arm h is in the verticalposition as shown, the field coils b" and b are oppositely andsubstantially equall y excited,

so that the eleetromotivc forces of the generators B and Tisubstantially balance each other. At. such time no elcctromotiwl'orcc isimpressed on the arn|a tureof motor I) and said luotor is at astamhstill. When the arm h movcs to one side of the 'crtical the speedof the motor I) in on dircclion is controlled, and when said arm ismovcd on thc other side of the vertical, the speed of said motor n theother dircction is controlled.

Between thc segnu-nts o and 9, and Ill and ll. of the controller arearranged resistances l2 and lil respectively, to take up the liclddischarge as the circuits through the coils b and I) are respectivelybroken. The resistances l2 and I?) are aided in this by high rcsistancesl9 and 2f) rcspeclivcly pernmnently connectcd across the coils b and brespectively.

Non-inductive resistanecs 2i and 22 are connected in series respectivelywith the coils I) and 0-2 These resistances have ohmic values severaltimes as great as those of the field coils with which they arercspcctively in series, and their purpose is to diminish the timeconstant of the field nmgncls b and b; for the time constant of acircuit is a function of its inductance divided by its resistance.'lhcrclorc by increasing the resistance of the iicld circuit vrithoutincreasing its inductance, the current strength being kcpt the same. thetime constant of the field magnet is reduced. By this means quickvariations in speed of the motor I) may he more readily obtained.

The OPUIZIlL'lOH of the system is as followsz The pri mary circuit ofmotor A. is closed. and the motor is started by moving the bar 2 to cutout the startingresistance l. The switch 4 is held open by its solenoidat this time because of the heavy current required for starting themotor. If desired other means maybe used to insure the open condition ofthis switch during start.- ing. After the motor has gained sullieientspeed and the starting resistance has been cut out, the solenoid switch4 is allowed to close to cut out resistance 3 because of the decrease inthe primary current of motor A, The fly-wheel U and generator armaturesll and I3 are started with the motor A. and the fly-wheel stores I]](chanical energy by its rotation. During this starting the arm it ispreferably in its vertical or oft position The switch 6 now beingclosed, the hold coils b, I) and (l are energized, the two generatorfield coils being oppositely and substantially equally excited. The electromotive forces of generators l1 and 13 counteract each other and nocurrent flows through the armature D oi the working motor. The arm It isnow gradually moved from the vertical toward the horizontal in theproper direction to give the motor D the desired direction of rotation.As this arm moves, say comiter-clockwise, it first inversely varies theresistances 14 and 16, thus weakening the field magnet b andstrengthening the field inagnetb As theresultof this, the electromotiveforce of D exceeds that of B, and the difference between, or algebraicsum of, these electromotive forces is impressed on the motor armature D.As the arm h continues to move, the resistance 14 is completely cut outraising the electromotive force of 13* to its maximum, while theresistance 16 is entirely cut in and the circuit of field coil b thenbroken. The field discharge due to this breaking is taken by theresistance 12 assisted by the resistance 19. The electromotive force ofthe generator B is now impressed upon the armature D. Farther movementof the arm 12 completes the circuit of field coil 1/ through the entireresistance l7, hilt the current in this ticld coil is now the reverse ofwhat it was prt viously. II the arm is moved still farther to the left,the resistance I7 is gradually cut out of circuit, thus increasing theelcctronlotivc force of the generator ll. During this lattcr part of themovement, the generators it and l5 assist each other, the sum of theirclcctromo tive forces ln-ing impressed upon the motolarlnat ure 1). Thespecd which the motor I) acquires depends upon the extent of movement ofthe arm /1. full speed being reached when the resistance IT has be nentirely cut out.

If the load is heavy, the working motor requires more power for itsstarting than the motor r\ can furnish The current rising in the primaryof the transformer 5 by reason of this heavy load, the switch f isopened. thus insert ing resistance 3 into the rotor circuit of motor A.This increases the slip of lnotor and permits said motor to slow down,thus allowing the fly-wheel to give up some of the mechanical energy it.has stored, which energy helps the motor A to drive the generators l1and 11 to supply electrical energy at the rate demanded by the motor l)to drive its load.

As the arm )1 is moved backward toward the vertical, the field I) isweakened. then reversed, and tin-ally strengthened toabout halfstrength, while thelield b is weakened to about half strength. All ofthis causes the algebraic sum of the electrtvinotive forces of the twogen Ul'itltll' iii-matures to be diminished. thus decreasing theelectromotivc force impressed on the armature of the motor I), causingthe latter to act as a generator to supply current to the armatures lland fl which now serve as motor armatures to help restore energy to thefly wheel (I. There is a powerful braking effect upon the working motordue to its acting as a generator. The diminished current in the primaryof transformer 5 also causes the solenoid switch 4 to close, therebyincreasing the speed of motor A so that it may also supply energy to theflywheel V. The fly-wheel thus stores up any excess of energy suppliedwhen the rate of such supply exceeds the rate at which energy isdemanded by the working motor. and gives up said stored energy wheneverthe rate of energy demanded is greater than the rate of energy supplied.When the arm h is moved in the other direction from the vertical theabove cycle is repeated save that the effects on the generators 11 andll are interchanged.

Whenever the arm it interrupts the field circuits of the generators theresistance 1201' I3 as the case may be is connected in circuit to takethe lield discharge, the resistance 19 or 20 assisting in this.

When I use theterm inversely in this description and in the claims, I donot wish to limit myself to exact inverse propm'tion but intend theterm. to include any increase in one and decrease in the other of thetwo things specified.

I have d +seribed my invention in what 1 new consider to be itspreferred form, but in the claims I aim to cover all those obviousmodifications which readily occur to one skilled in the art Having thusdescribed my invention, what I claim as new and desire to secure byLetters Patent is 1. The method of controlling the speed and directionof an electric motor. which consists in supplying its armature from twosources of current in series, said sources being normally approximatelyequal and opposite, and inversely varying the electromotlvc forces ofsaid two sources of current.

2. The method of controlling the speed oi an electric motor, whichconsists in supplying it from two sources of current in series, anddissimilar-lyvarying the electromotive forces of both of said sources.

3. The method of controlling the direction of rotation of an electricmotor, which consists in supplying its armature from two opposingsources at current in series, and varying the relation between theclcctroumtivc forces of said sources so that either of them maypredominate.

4. The method of reversing an electric motor, which consists insupplying its armature from two assisting sources of current in series,then diminishing, reversing and increasing the ciectromotive force ofone of said sources, and then diminishing, reversing and increasing theclectromotive lorce of the other source.

5. The method of reversing an electric motor, which consists insupplying its armature from two unequal opposing sources of current inseries. and then varying the relation between the electronmtive forcesof said two sources until the inequality is reversed.

(i. The method of controlling an electric motor, consisting in rotatinga plurality of generator armaturcs in separate magnetic fields,impressing the algebraic sum of the electro-motive forces of saidgenerator armatures on the armature of the motor, and varying all of themagnetic fields so that at times said algebraic sum is' less than one ofits components.

I. The method of controlling an electric motor, com slsting in rotatinga plurality of generator armatures in separate magnetic fields,impressing the algebraic sum of the electro-motive forces of saidgenerators-on the armature of the motor, and inversely varying two ofsaid generator fields.

S. The method of controlling an electric motor, consistlng in rotating aplurality of generator nrmatures in separate magnetic fields, impressingthe algebraic sum of the electro-motive forces of said generators on thearmature of the motor, and dllferently varying the fields of saidgenerators.

9. The method of controlling an electric motor, con sisting in rotatinga plurality of generator armatnres in separate magnetic fields,impressing the algebraic sum of the eiectro-motive forces of saidgenerator armnturcs upon the armature of the motor, and varying saidalga-- hraic sum from a maximum in one direction to a maximum in theother direction by successively reversing the magnetic fields of thevarious generator armatnres.

10. The method of operating an electric motor at variable speed and loadwhich consists in supplying mechanical energy, converting it intoelectrical energy at a pinrality of separate electro-motive forces,impressing the algebraic sum of said electromotlve forces on thearmature of the motor. and individually varying said componenteiectro-motive forces.

It. The method of operating an electric motor at varinhle speed and loadwhich consists in supplying mechanical energy, converting it intoelectrical energy at a pin raiity of separate elcctro-motive forces,impressing the algebraic sum of said eiectromotive forces on the arms'ture of the motor, individually varying said component eiectromotiveforces, storing any excess of mechanical energy supplied when its rateof supply exceeds the rate at which energy is demanded by the load, andsupplying said stored energy to the motor as electrical energywhenencrgy is demanded by the load at a rate which exceeds the rate atwhich the mechanical energy is supplied.

1;. A system of distribution, comprising a plurality of dynamo-electricgenerators drive by a source of sub srantially constant power, means forinversely varying the electromotive forces of two of said generators,and

means for mechanically storing any excess of energy sup" plied by thedriving source and supplyime said stored energy to help drive thegenerators whenever required.

13, A system of motor control, comprising a plurality of dynaluweicctrlcgenerators. a motor supplied thereby. means for dillorcntly varying theelectromutire forces, of said generators. means for storing an) excessof mechanical energy supplied to the generators when its rate of supplyexceeds the power demanded by the motor at that time. and means fordausing said stored energy to he sup plied to the motor whenever thepower demanded by the motor is above that normally supplied.

14. A system of motor control, comprising a motor, two sources ofcurrent connected in series for supplying the motor armature, and meansfor varying and reversing the ciectromutivc force of each of saidsources oi. current.

15. A motor control system comprising two dynamoclcctricgenerators, amotor whose armature has impressed thereon the algebraic sum or theeiectromotive forces of said generators, and means for inversely varyingsaid component electro-motive forces.

16. A motor control system comprising two dynamocicctric generators, amotor the armature of which is supplied by said generators in series,and means for diitercntly varying the field strengths of saidgenerators.

17. A system of motor control, comprising an electric hunt, a pluralityof sources of current connected in series and supplying the motorarmature, and means for sucl ssively diminishing to zero and increasingin the reverse direction the clcctromotive forces of said sources ofcurrent.

IS. A motor control system, comprising a source of mechanical power, aplurality, of generators driven there lip-said generators beingconnected in series, a motor supplied by said generators, means fordilferently varying the electro-motive forces of said generators, meansfor storing; any excess of mechanical energy supplied by said sourcewhen its rate of supply exceeds the rate at which energy is demanded bythe motor load, and means for causing said stored energy to be suppliedto the motor as electrical energy when energy is demanded by the motorload at a rate which exceeds the rate at which mechanical energy issupplied by the source.

19. in combination, a source of power, a plurality of generators driventhereby and connected in series to sup ply a motor, means fordifferent-B varying thefieiu strengths of said generators, a fly-wheelmechanically connected to said generators, and means for causing thefly-wheel to give up its energy when the load on the motor rises abovethe normal.

20. In combination, a source of power, two generators driven thereby, amotor supplied by said generators in series, means for inversely varyingthe resistances of the field circuits of said generators, a fly-wheelmechanically connected to said generators, and means for allowing saidfly-wheel to give up its energy when the motor load rises above normal.

21. A system of motor control comprising a motor, a plurality ofgenerators supplying said motor, a. fiy-wheel mechanically connected tosaid generators, and means for successively reversing the fields of saidgenerators.

22. A system of motor control, comprising a motor, two generatorsconnected in series for supplying the armature of said motor, and meansfor inversely varying the field strengths of said generators and forreversing the field which is weakened.

23. In a system of distribution, a translating device, a plumllty ofsources of current connected in series for sup-' plying said translatingdevice, and means for successively reversing the electro motlve forcesof said sources of current.

24. In a system of distribution, a translating device, a plurality ofgenerators connected in series and supplying said translating device,and-means for varying the field strengths of said generators so that thegenerators oppose each other, or assist each other in either direction.

25. A system of motor control, comprising an induction motor, twogenerators driven thereby, a fly-wheei mechanically connected to -aaidinduction motor, a working motor whose armature is supplied by said twogenerators connected in series, and unitary means for varying the fieldstrengths of all of said generators. 7

26. system of distribution, comprising a translating device, a pluralityof generators connected in series and supplying said translating device,and a unitary means for varying and reversing the Fields of all of saidgenerators.

27. A system oi distribution, comprising a translating: device, aplurality of generators connected in series and supplying saidtranslating device, and a unitary means for varying the fields of all ofsaid generators and for reversing said tields at (litter-cut. points inits movement.

28. A system of motor control, comprising a source ot current, a motorsnpplied iilierehy, a tly-wheel mechanically connected to said motor,two generators driven by said motor and connected in series to supply asecond motor. and means for inversely varying the field strengths ofsaid generators and for reversing the tield of either of them.

29. A system of motor control, comprising a plurality of generatorsconnected in series and supplying a motor, means for varying the tieldstrengths of said generators. and resistances permanently in saidrespective generator tield circuits.

Jill. A system of motor control. comprising :1 motor supplied by aplurality of generators connected in series, resistances in the fieldcircuit of each of said generators. means for varying said resistancesand for reversing; the current in said respective generator fieldcircuits after their associated resistances have been fully cut in, anda high resistance permanently connected across the tield tcrminals ofeach generator.

I: A system of motor control, comprising a plurality of generatorsconnected in series and supplying a motor, means for IQVOl'Silli: toefield magnetism of said genera tors, and a high resistance permanentlyconnected across the iield terminals of each generator.

32. A system of motor control comprising a source of current supply, amotor supplied thereby, a plurality of generators driven by said motor,a lly-wheel mechanically connected to said generators, a second motorthe armature of which is supplied by said generators jointly, and meansfor permitting the first motor to slow down upon an increase in the loadon the second motor.

:53. system of motor control, comprising a source of current supply, amotor supplied thereby, a plurality of generators driven hy saiu motor,a fly-wheel mechanically connected to said generators, a second motorthe armature of which is supplied by said generators in series. andmeans for causing said first motor to increase in speed upon decrease inload on the second motor.

in testimony whereof I aflix my signature, in the pres ence of twowitnesses.

WILLIAM H. POWELL.

Witnesses (ti-1o. I Scum-n, Flu-m J. Kisser.

